plants, animals, and bacteria all have had important roles in the present composition of our atmosphere. Without life, the atmosphere would be very different. It’s possible that such an atmosphere would not be able to shield the surface of the Earth against solar winds and ultraviolet rays, and the oceans would evaporate. Soon, greenhouse effects would turn the Earth’s atmosphere into a copy of Venus’s, and then water vapor would be lost to space over time. After several billion years, the Earth would be dry.”
